This invention relates to drill pipe handling apparatus, and more particularly to drill pipe handling apparatus used for off vertical drilling.
The invention is especially concerned with drill pipe handling apparatus in which a plurality of drill pipes are held in a magazine and successively fed into the drilling apparatus. The magazine of the handling apparatus has a center shaft and upper and lower heads which hold the drill pipes around the shaft. The magazine is rotated about the shaft to bring the next drill pipe into position for feeding into the drilling apparatus. The entire magazine is swung into the drilling apparatus to feed the positioned drill pipe to the drilling apparatus. The drilling apparatus is positioned at an angle off vertical for drilling at an angle and, therefore, the magazine is positioned at an angle off vertical so that the pipes will be properly aligned when fed into drilling apparatus. When the magazine is fully loaded with drill pipes, it is balanced for relatively easy control despite the great weight of the pipes. However, once one of the pipes is removed, the magazine becomes unbalanced causing the magazine to tend to rotate too far and misalign the next drill pipe. Drilling is delayed while the magazine is rotated completely around the center shaft to position the pipe after over-rotation occurs. Frequently, several attempts must be made before the pipe is properly positioned. One approach for preventing such over-rotation of the magazine has been to provide braking means for the magazine shaft, but the braking means which has been used has had the problem of being unable effectively to hold the shaft against rotation, particularly when the shaft is wet or oily as it often is, and of braking or jamming the handling apparatus if tightened in an effort to hold the shaft.